一类无人直升机的旋翼操纵机构的分析

基于目前应用极为广泛一类无人直升机,论述了它的旋翼操纵机构,特别是对它的主旋翼和稳定杆的动力学特性进行了详尽描述,通过对它们的动力特性分析为以后建立无人直升机的六自由度运动方程打下了基础。     

自主无人直升机桨叶挠变挥舞运动动力学建模

某30kg级自主无人直升机的跷跷板结构主旋翼是挠性的。针对该直升机,基于达朗伯原理建立绕自由空间点转动的桨叶挠变挥舞运动动力学模型,并借鉴悬臂梁受力挠变处理方法给出了桨叶挠变方程。数值仿真验证了桨叶挠变挥舞运动动力学模型的正确性。     

一种用于微小型无人直升机试验研究的6自由度支撑平台

针对微小型无人直升机动力学建模与控制实验的安全问题,避免在实验或测试中造成人员伤害和直升机及其机载设备的损毁,设计了一种被动式微小型无人直升机6自由度支撑平台。该平台由具有被动重力平衡能力的平行四边形机构组成,无人直升机与平台之间采用球铰连接,从而使得直升机能够在所允许的范围内作任意方向的飞行、姿态机动或悬停在任意位置而不受支撑平台重力的影响,能够满足无人直升机在实际运动过程中全部6个自由度仿真的需求。为了评价机构的重力平衡效果,在ADAMS环境下对支撑平台系统进行了动力学仿真,并给出了仿真结果。评估了支撑平台设计方案的优缺点,以及在实际实际使用过程中需要注意的问题。研究结果表明,该方案结构简单、实施方便,能够有效保障微小型无人直升机动力学建模与控制实验的安全。     

一种共轴双旋翼无人直升机旋翼及操纵系统设计

文中对共轴双旋翼无人直升机旋翼系统进行剖析,参考通航共轴双旋翼直升机的旋翼系统设计经验,结合无人直升机的特性,确定旋翼及操纵优化设计思路.根据共轴双旋翼无人直升机的总体参数,计算分析旋翼系统关键结构件的受力情况,进行旋翼系统机构设计并对关键件进行强度分析.通过使用动力学分析软件,分析旋翼及操纵系统的控制方式,对旋翼及操...     

基于空间多点悬挂机载云台的轻量化设计分析

多轴增稳云台作为小型无人飞行器载荷系统重要的组成单元,小型化、轻量化与高集成化是云台设计发展的基本趋势之一。提出了一种基于空间多点悬挂、多轴系框架闭环的云台系统轻量化设计方法,分析了封闭环架多点自由度约束设计模型,通过载荷的力矩计算,创建了云台系统的轻量化模型。通过有限元力学建模仿真,结合多旋翼无人飞行器的振动特性,与实验相结合,分析了云台系统的振动特性和随着载荷重量改变的模态响应,验证了系统设计的可行性和稳定性,为云台系统的轻量化设计提供了理论参考。     

小型无人直升机自转建模与控制策略研究

针对小型无人直升机动力失效后的自转着陆问题,建立了直升机自转飞行动力学模型。根据直升机自转飞行过程中的下降速度变化,将飞行过程分为加速下降、稳定下降和减速着陆 3 个阶段,设计了相应的控制策略。仿真结果表明,该模型具有较高的精度,实现了直升机自转飞行的安全着陆。研究成果对小型无人直升机自转飞行的研究具有一定的参考意义。     

无人直升机主减中两级变速齿轮传动构型方案概述

无人直升机为了实现经济性巡航,需要改变主旋翼转速。目前,改变主旋翼转速,实现大调速范围和成本低的最有效方法为主传动系统采用变速齿轮传动。因此,针对起飞和巡航时无人直升机主旋翼的转速差异,国外已开展无人直升机两级变速传动系统的研究和应用。本文根据有限的国外文献资料,对无人直升机两级变速齿轮传动构型进行整理,以期促进我国无人直升机变速传动机构的发展。     

共轴双旋翼高速直升机主减轮系功率流向分析

研究了一种共轴式反转的高速直升机主减轮系方案,为设计者提供了一种快速判断轮系功率流向的方法。首先,将轮系单元分析法引入共轴双旋翼高速直升机主减轮系的分析,并完成直升机主减轮系的数学建模。然后,总结出共轴双旋翼高速直升机主减轮系方案所有可能的功率流向类型。最后,研究了共轴双旋翼高速直升机主减轮系的功率流向类型及其不同的飞行状态(前飞、改变航向等)对主减轮系效率的影响。     

直升机某旋翼试验台模态分析与试验

直升机旋翼试验台的动特性可直接影响旋翼动力学试验时的测试精度与性能。研究相应准确识别手段,能够为直升机旋翼试验评估与使用管理提供依据。在有限元仿真的基础上,准确简化模拟试验台数值模型,计算得出试验最优结构测点与激励点,通过对优化后的试验模型进行模态试验分析,得出旋翼试验台的固有频率与振型。结果表明,采用有限元分析能够有效提高模态试验的精度,达到快速准确识别试验台固有频率的效果和整体结构刚度的合理匹配。     

可变结构小型多旋翼无人飞行器的设计

针对现有的四旋翼直升机存在飞行速度低、航程短等问题,综合考虑了四旋翼可以垂直起降和固定翼能够长距离航行的特点,提出一种在四旋翼的基础上添加一对固定翼和涡扇推力电机的变结构无人飞行器,并给出三维建模;在水平飞行时机身两侧的双涵道涡扇和机翼共同向前倾斜以产生向后的推力和向上的升力。开发出该变结构无人飞行器样机,对飞行器固定翼进行流固耦合力学仿真分析,最后对变结构飞行器动力学建模。固定翼的单向流固耦合计算结果显示,设计的机翼升力满足设计要求。从截面翼型位置上分析有一定意义,证明最大应力并非在翼型的前缘或后缘,而是在上表面,同时也验证了CLARK Y翼面形状产生的升力在飞行过程中起主要作用。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.